DESCRIPTION: RecA is a bacterial protein that functions in at least two ways to repair DNA damage. First, it has a DNA strand exchange activity that catalyzes recombinational DNA repair. Second, it has a coprotease activity that regulates the expression of SOS genes which also are involved in DNA repair. The primary goal of this work is to determine the molecular basis underlying RecA-dependent DNA repair. The proposed research involves the use of genetic, molecular biological, biochemical and protein design techniques aimed at defining both RecA-specific repair events, as well as functional interactions between RecA protein and other SOS gene products that contribute to the overall process of DNA repair. This investigator has devised a genetic system in which expression of the RecA gene is controlled by Ptac, thereby removing RecA from the autoregulatory SOS pathway. This system has allowed the identification of mutants with distinct split phenotypes which will facilitate in the dissection of this repair pathway.